In the related art, a fluid control system is known which includes a vacuum chamber, a gas supply source for supplying a gas to the vacuum chamber, a gas supply pipe installed to connect the vacuum chamber and the gas supply source, a pressure sensor for detecting an internal pressure of the vacuum chamber, a pressure controller for controlling a proportional valve installed in the gas supply pipe based on an output provided from the pressure sensor; a flowmeter installed in the gas supply pipe, and a flow rate controller for controlling a throttle valve installed in an exhaust pipe based on an output provided from the flowmeter. In such a fluid control system, the pressure controller and the flow rate controller are installed independently of each other. The internal pressure of the vacuum chamber is controlled by the pressure controller. A flow rate of a process gas flowing to the vacuum chamber is controlled by the flow rate controller through the use of the throttle valve installed in the exhaust pipe.
Furthermore, a film forming apparatus has been used which forms a thin film on a substrate within a reaction chamber by alternately supplying a raw material gas and a reaction gas which reacts with the raw material gas to generate a reaction product, to the reaction chamber under vacuum atmosphere. The film forming apparatus includes: a raw material gas supply path through which the raw material gas is supplied into the reaction chamber; a tank installed in the middle of the raw material gas supply path and that stores the raw material gas with an increased pressure; and a flow rate regulating valve installed in the raw material gas supply path at the downstream side of the tank. The film forming apparatus is configured to supply a large amount of the raw material gas into the reaction chamber through the tank in a short period of time. The flow rate regulating valve installed in the raw material gas supply path at the downstream side of the tank is a valve capable of regulating a set flow rate thereof. However, the flow rate regulating valve performs only opening and closing operations and does not control an opening degree thereof in real time.
However, in the conventional fluid control system, a pressure and a flow rate are controlled independently of each other. Such pressure and flow rate are correlated with each other and influence each other. As such, clogging is more likely to occur while the pressure and the flow rate are being independently controlled. Furthermore, the conventional fluid control system requires both the pressure controller and the flow rate controller, which results in an increase in size of the system and an increase in cost.
The conventional film forming apparatus is effective in supplying a large amount of raw material gas into the reaction chamber in a short period of time. However, since the flow rate of the raw material gas supplied into the reaction chamber from the tank is not feedback-controlled, the conventional film forming apparatus may be not sufficient to meet the requirement of supplying a large amount of raw material gas in a short period of time while controlling the flow rate in real time.